Physical vapor deposition (PVD) is a known film deposition technique that entails heating a material in a vacuum to a temperature at which the material vaporizes and then condenses on a relatively cooler substrate. For various reasons, metallic and ceramic coatings for gas turbine engine components are often deposited by PVD. For example, electron beam physical vapor deposition (EBPVD) is used to produce a desirable columnar grain structure for ceramic topcoat layers of thermal barrier coating (TBC) systems. The ceramic material often preferred is yttria-stabilized zirconia (YSZ), which must be heated to about 4000 K to about 4300 K to produce a YSZ vapor that subsequently condenses on the component.
Gas turbine engine components typically sustain temperatures in excess of 1700.degree. F. (about 927.degree. C.) during coating by PVD. As a result of stringent requirements to control temperature uniformity during the coating cycle, a "working zone" is typically established in the PVD coating chamber within which sufficient temperature and coating vapor uniformity can be maintained to meet processing requirements. Components to be coated must be held and manipulated in the working zone of the coating chamber using complex tooling and fixturing. As a result, this tooling and fixturing is exposed to the same elevated temperatures seen by the components receiving the PVD coating, necessitating that the tooling and fixturing be fabricated from materials that can survive the high-temperature coating environment of a PVD coating chamber. Notable examples are the gears required to rotate components in order to deposit by EBPVD a ceramic layer with a columnar grain structure.
Though high-temperature materials are used to form the tooling and fixturing, repetitive high-temperature exposures and associated thermal cycling results in physical degradation of these components, which necessitates their replacement on a routine basis. Because of the costs associated with their complexity and high temperature capability, it would be desirable if the frequency of replacing PVD components, tooling and fixturing could be reduced.